
/* @(#)w_exp.c 5.1 93/09/24 */
/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

/*
FUNCTION
    <<exp>>, <<expf>>---exponential
INDEX
    exp
INDEX
    expf

ANSI_SYNOPSIS
    #include <math.h>
    double exp(double <[x]>);
    float expf(float <[x]>);

TRAD_SYNOPSIS
    #include <math.h>
    double exp(<[x]>);
    double <[x]>;

    float expf(<[x]>);
    float <[x]>;

DESCRIPTION
    <<exp>> and <<expf>> calculate the exponential of <[x]>, that is,
    @ifnottex
    e raised to the power <[x]> (where e
    @end ifnottex
    @tex
    $e^x$ (where $e$
    @end tex
    is the base of the natural system of logarithms, approximately 2.71828).

    You can use the (non-ANSI) function <<matherr>> to specify
    error handling for these functions.

RETURNS
    On success, <<exp>> and <<expf>> return the calculated value.
    If the result underflows, the returned value is <<0>>.  If the
    result overflows, the returned value is <<HUGE_VAL>>.  In
    either case, <<errno>> is set to <<ERANGE>>.

PORTABILITY
    <<exp>> is ANSI C.  <<expf>> is an extension.

*/

/*
 * wrapper exp(x)
 */

#include "fdlibm.h"
#include <errno.h>

#ifndef _DOUBLE_IS_32BITS

#ifdef __STDC__
static const double
#else
static double
#endif
o_threshold=  7.09782712893383973096e+02,  /* 0x40862E42, 0xFEFA39EF */
u_threshold= -7.45133219101941108420e+02;  /* 0xc0874910, 0xD52D3051 */

#ifdef __STDC__
    double exp(double x)        /* wrapper exp */
#else
    double exp(x)           /* wrapper exp */
    double x;
#endif
{
#ifdef _IEEE_LIBM
    return __ieee754_exp(x);
#else
    double z;
    struct exception exc;
    z = __ieee754_exp(x);
    if(_LIB_VERSION == _IEEE_) return z;
    if(finite(x)) {
        if(x>o_threshold) {
        /* exp(finite) overflow */
#ifndef HUGE_VAL
#define HUGE_VAL inf
            double inf = 0.0;

            SET_HIGH_WORD(inf,0x7ff00000);  /* set inf to infinite */
#endif
        exc.type = OVERFLOW;
        exc.name = "exp";
        exc.err = 0;
        exc.arg1 = exc.arg2 = x;
        if (_LIB_VERSION == _SVID_)
          exc.retval = HUGE;
        else
          exc.retval = HUGE_VAL;
        if (_LIB_VERSION == _POSIX_)
          Djy_SaveLastError(ERANGE);
        else if (!matherr(&exc)) {
            Djy_SaveLastError(ERANGE);
        }
            if (exc.err != 0)
               Djy_SaveLastError(exc.err);
            return exc.retval;
        } else if(x<u_threshold) {
        /* exp(finite) underflow */
        exc.type = UNDERFLOW;
        exc.name = "exp";
        exc.err = 0;
        exc.arg1 = exc.arg2 = x;
        exc.retval = 0.0;
        if (_LIB_VERSION == _POSIX_)
          Djy_SaveLastError(ERANGE);
        else if (!matherr(&exc)) {
            Djy_SaveLastError(ERANGE);
        }
            if (exc.err != 0)
               Djy_SaveLastError(exc.err);
            return exc.retval;
        }
    }
    return z;
#endif
}

#endif /* defined(_DOUBLE_IS_32BITS) */
